I've recently developed an interest in critical hits, and I'm looking to create the largest critical multiplier possible. Note that I'm not asking about critical threat range - I'm familiar with that - but rather the actual damage multiplier at the end. So, what resources are available to increase this multiplier? I'm already familiar with the Nightmare Blade maneuver line (a godsend for huge crits), but I'm definitely in the market for others.

Kaorti resin gets you auto-×4 on any piercing or slashing weapon you use it to make, so that’s an obvious choice when combined with a weapon that gets 18-20 crit range, or on a Lance for the freebie ×2 on charges (total ×5 on charge-crit). Other general multipliers, like Leap Attack, may also be useful. See an ubercharger handbook for a good list of those